Small Form Factor Connectors Cut LAN Costs

There is great news in fiber optics. The world of optical waveguides, also known as fiber optic communications, is entering a significant transition. At least 11 factors drive this transition, one of which is the small form factor (SFF) connector, which is affecting the cost of fiber optic local area networks (LANs) significantly, and for the good.

These two-fiber connectors are small, the size of the ubiquitous and well-received RJ-45, making the transition to the SFF less of a psychological shift than that of going to the common ST-compatible and SC designs.

The hope of significant reductions in fiber optic network costs is influencing the transition to the SFF connector. These costs would drop at hubs, switches, patch panels, enclosures, jumpers, and in the SFF connectors themselves.

The cost reduces at hubs and switches because the two fibers are so close together. Hub and switch manufacturers can double port density and reduce the cost per port. Already, the cost of SFF 100Base-F switch ports is now below $170 and that of the companion network interface cards (NICs) (IS THAT A GOOD GUESS?) is below $120. These compare favorably in cost with ST-compatible switches at approximately $200 per port and their NICs at $190.

The cost reduces again at patch panels and enclosures, for the same reason: the close spacing of the fiber. This spacing enables doubling the densities, cutting the costs per port in half. (AGAIN, GUESSING. IS THIS WHAT YOU MEANT?)

Some of the SFF jumpers (the Opti-Jack from Panduit and the MT-RJ from Siecor and AMP) are cheaper than SC jumpers. Other SFF jumpers, such as Volition, are less expensive than the ST-compatible jumpers are. (FOR THOSE OF US NOT BUYING THESE JUMPERS, ARE ST OR SC MORE EXPENSIVE?)
One SFF Volition distributor currently offers connectors that cost less than either ST-compatible or SC connectors.

Additional great news comes from the standards front. The TR-42.1 committee has approved revising the TIA/EIA-568A standard to allow using the SFF connectors. Before this proposal was approved, complying with the Building Wiring Standard required using the SC connector.

In addition, this revision will incorporate a 300m recommendation for a fiber-to-the-desk, collapsed backbone configuration. This configuration offers the possibility of a pure fiber optic LAN with a cost equal to, and perhaps less than, that of the currently accepted unshielded twisted pair (UTP)/fiber optic mixed-media configuration. Some of this cost break will come from eliminating the cost factors in the wiring closets. These closets will not need switches, hubs, UPSs, surge protection, and environmental controls. (WHY?)

So much for the purely good news. The rest is mixed.

The competitive situation is certainly mixed. There are six SFF designs to choose from: Opti-Jack, MT-RJ, Volition, LC, LX.5, and MU. These designs offer the opportunity to choose the product best suited to the application; however, the number of choices may create confusion for the designer, installer, and user.

Each of these designs offers different features and benefits. The Opti Jack, from Panduit Corporation, (HYPHENATE, AS ABOVE, OR NOT?) the most rugged of the six designs, is based on three existing, well-developed, and well-accepted technologies (Figure 1). This plug-and-jack family uses the 2.5-mm ceramic ferrule, the split alignment sleeve, and quick-cure adhesive. The 2.5-mm ferrule has been used for the last 13 years in five designs: ST-compatible, SC, FC, MIC, FDDI, and ESCON. The split alignment sleeve is used in all these designs.

The quick-cure adhesives have been in use for the last seven years. The Opti-Jack is a complete connector system, with 62.5 µm and 50 µm multimode and single-mode plugs and jacks available. All plugs and jacks can be installed in the field.

The MT-RJ, available from AMP, Siecor, and others, has the most support among electronics manufacturers. (See Figure 2.) It is one of the fastest to install, since the jack is prepolished. Unfortunately, not all its components are available or can be installed in the field.

The Volition, from 3M, is the cost leader among SFFs. Its connectors, jumpers, switches, and hubs cost the least in the fiber industry. (See Figure 3.) A preliminary analysis from Pearson Technologies Inc. provides the following comparison: a Volition, 100Base-F collapsed-backbone fiber-to-the-desk network has a cost of $500 per node, while using UTP cable to the wiring closet with a fiber vertical-backbone network has a partial cost of $408 per node. However, if we add surge suppression, UPS, and environmental costs to the UTP wiring closet, the UTP fiber optic network could well be more expensive that the FTTD LAN. (AGAIN, I DO NOT UNDERSTAND. DOES VOLITION INHERENTLY PROVIDE SURGE SUPRESSION, UPS, AND ENVIRONMENTAL COSTS? IF SO, WHY ISN'T THAT IN THE STORY? IF NOT, WHAT IS THE RELEVANCE HERE?)

The Volition is based on a new concept: Using precision V-grooves to provide low optical power loss. All other SFF connectors use ferrules.

The LC, developed by Lucent Technologies, has respectable support from electronic manufacturers. However, it is not a true two-fiber connector. Rather, it is a single-fiber connector that can be clipped to another to form a duplex.

The LC can use epoxy or quick-cure adhesives for installation. The LC is not the preferred plug-and-jack configuration, as are the Opti-Jack, MT-RJ, and Volition. The LC uses the legacy plug adapter plug configuration.

The LC also uses a 1.25-mm ferrule, which might result in problems during field installation. Polishing this 1.25-mm ferrule by hand may be more difficult than polishing 2.5-mm ferrules, since the pressure must be quadrupled.

The LX.5, from ADC Telecommunications, also uses the 1.25-mm ferrule. This product has a built-in dust cover in the plug, but it is not the preferred plug-and-jack configuration.

The MU looks like a half-size SC. This product, which also uses the 1.25-mm ferrule, is not the preferred plug-and-jack configuration. There are no MU manufacturers in North America. However, this design is popular in Japan and Europe.

The SFF, by itself, may not produce a cost analysis that favors the pure fiber optic LAN. However, other factors are also reducing fiber optic LAN costs. As we refine our analyses to include factors, we will report the results.

To date, data on the SFF connector's performance suggests that using FTTD and increasing fiber use may be justified.

BIO:

PEARSON, president of Pearson Technologies Inc., and a certified professional consultant (CPC) specializes in fiber optic communications, providing technical, business, and legal consulting in fiber optics and training on designing and installing fiber networks. He is an editorial advisor to Fiberoptic Product News, is the director of certification and a member of the board of directors of the Fiber Optic Association, and has written The Complete Guide to Fiber Optic Cable System Installation (Delmar Publishing, 1997]) He may be reached at fibrxpert@aol.com.

Possible pull quotes:
These designs offer the opportunity to choose the product best suited to the application; however, the number of choices may create confusion for the designer, installer, and user.